Multiple stage mast structure



June 6, 1961 J. E. OLSON MULTIPLE STAGE MAST STRUCTURE 4 Sheets-Sheet 1 Filed Sept. 15, 1958 INVENTOR.

JOHN E. OLSON lli-III BY Buck/70m, C/760/h0/7; 8 5/0/19 ATTORNEYS June 6, 1961 J. E. OLSON 2,987,140

MULTIPLE STAGE MAST STRUCTURE Filed Sept. 15, 1958 4 Sheets-Sheet 2 INVENTOR. JOHN E. OLSON BY Buck/70m, C/76C7f/I0/77, 8r B/ore AT TORNE Y3 June 6, 1.961 J. E. OLSON MULTIPLE STAGE MAST STRUCTURE 4 Sheets-Sheet 5 Filed Sept. 15, 1958 INVENTOR. JOHN E. OLSON Bud/70m, Chem/1am, 8 Blame ATTORNEYS June 6, 1961 J. E. OLSON MULTIPLE STAGE MAST STRUCTURE 4 Sheets-Sheet 4 Filed Sept. 15, 1958 INVENTOR.

JOHN E. OLSON BY Buck/10m, Chad/ham, & B/ore ATTORNEYS United States Patent 2,987,140 MULTIPLE STAGE MAST STRUCTURE John E. Olson, Portland, 0reg., assignor to HysterCom- This invention relates to extensible mast structures and particularly to extensible mast structures for industrial lift trucks. The present application is co pending with my prior applications entitled Free Lift Truck Serial No. 543,822, filed October 31, 1955, now Patent No. 2,915,144, and Free Lift Cylinder Serial No. 722,092, filed March 17, 1958.

Mast structures which are very short in their collapsed condition but of considerable height when in their extended condition are not new, one being shown, for instance, in the patent to Weaver 2,480,066. Such structures are generally referred to as multiple stage mast structurues because the mast is extended by the relative movement of more than two telescopic mast sections. Prior multiple stage mast structures have been complicated, have frequently required multiple rams, and many such structures have been unreliable in that the mast sections do not descend in the proper order thus allowing dropping of a load for a limited distance and subjecting the mast structure to considerable shock and strain.

It is a main object of the present invention to provide a multiple stage mast structure which is simple and inexpensive as compared to prior multiple stage mast structures.

Another object of the invention is to provide a multiple stage mast structure which is reliable in operation and in which the sequence of movement 0 the mast parts is reliable.

A further object of the invention is to provide a multiple stage mast structure including only a single compound ram which is operable to elevate the load extend the mast.

A still further object of the invention is to provide a multiple stage mast structure in which the ram is concarriage and nected only to the load carriage and the mast section which the carriage engages, to thereby greatly simplify the construction of the mast structure.

Another object of the invention is to provide a multiple stage mast structure having a novel latch means for connecting the load carriage to the upper end of the mast structure along which it rides, and also having a novel latch means for connecting the just mentioned mast section to the adjacent mast section during extension of the mast.

Various other objects of the invention will be apparent from the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a side view in elevation of a mast structure of the invention, showing the lift chains diagrammatically;

FIG. 2 is a front view of the mast structure, the chains being left out for convenience in illustration, and the load carriage being removed for the same reason;

FIG. 3 is a top view of the mast structure on a scale larger than that employed in FIGS. 1 and 2, the chains being left out for convenience in illustration, but the load carriage being employed;

FIG. ,4 is a vertical section taken along lines 4-4 of FIG. 3 showing the carriage latch mechanism, the view being taken on a scale somewhat larger than that em- FIG. 7 is a view similar to FIG. 6 showing a subsequent stage of operation;

FIG. 8 is a view on an enlarged scale of the carriage latch mechanism, and showing the mechanism with the parts in the condition they occupy when the mast is extended as shown in FIG. 7;

FIG. 9 is a view similar to FIG. 8 showing a subsequent stage of operation of the carriage latch mechanism;

FIG. 10 is a view similar to FIG. 7 but showing a still subsequent stage of operation; I FIG. 11 is a view on an enlarged scale of the mast section latch mechanism showing the parts in the positions they occupy when the mast is extended substantially as shown in FIG. 10;

FIG. 12 is a view similar to FIG. 11 but showing a subsequent stage of operation of the mast section latch mechanism; and

FIG. 13 is a view similar to FIG. 10 showing the final stage of extension of the mast, this view taken on a some what reduced scale from that employed in FIG. 10 for convenience in illustration.

General description Referring to FIGS. 2, 3 and 6, the mast structure includes an outer section 11, an intermediate section 13 and an inner section 15 which are telescopically related for extension and contraction. In the form of the invention shown, each mast section comprises a pair of spaced channels joined by various connecting pieces and braces. For convenience, the channels will be assigned the reference numerals employed in connection with the associated section, while the braces and connecting pieces will be given diiferent reference numerals.

A single compound ram is provided and includes a plunger 17 resting on the lower end of the outer mast section 11, an intermediate cylinder 19 surrounding the plunger and carrying a crosshead 2 1, and an outer cylinder 23 surrounding the intermediate cylinder and having its upper end in thrust engagement with the upper end of inner mast section 15.

Referring to FIGS. 1 and 6, a chain and sheave type motion multiplying mechanism 25 interconnects the ram and the inner mast section 15 and also a load carriage 27 which movably engages the inner mast section.

Brief description of operation In order that the detailed description of the mast structure will be understood more readily, a brief description of the operation of the mast structure will be given without reference to details.

Referring to FIG. 6, when fluid under pressure is supplied to the ram, the intermediate cylinder 19 moves downwardly to the phantom line position shown for the crosshead to raise the load carriage at a 2 to 1 rate to its phantom line position shown in FIG. 6. There is no extension of themast under these conditions, and thus there is free lift of the carriage from its full line position in Fig. 6 to its phantom line position. By free lift, it is meant elevation of the carriage without extension of the mast.

Referring to FIG. 7, the outer cylinder 23 then moves upwardly, raising the inner mast section '15 because of its direct engagement therewith and to raise the load carriage at a 2 to 1 rate to move the load carriage to the full line position shown in FIG. 7 where it is disposed at the upper end of the inner mast section 15.

There is a latch mechanism 29 which latches the inner mast section 15 to the upper end of the outer cylinder .23, and the load carriage 27 engages this latch mechanism when the load carriage reaches the upper end of the inner mast section to release the inner mast section for upward movement. Substantially simultaneously with such release, the carriage is latched by such latch mechanism to the inner mast section for movement upwardly therewith in unison.

Referring to FIG. 10, the outer' cylinder 23' continues its upward movement, but since the inner mast section 15 is released from the ram, this continued upward movement of the outer cylinder raises the inner mast section at a 3 to 1 rate to a position where a brace 31 on the inner mast section 15 engages a stop 33 on the intermediate mast section 13. This lifts the intermediate mast section and simultaneously actuates a mast section latch mechanism 35 which latches the intermediate mast section at its upper end to the brace 31 of the inner mast section 15. Thus, the inner mast section 15 cannot move downwardly relative to the intermediate mast section until the latch mechanism 35 is released.

In the FIG. position of the parts, it is apparent that a stop 37 on the lower end of the outer cylinder 23 engages a stop 39 on the upper end of the intermediate cylinder 19, and thus the outer cylinder and the intermediate cylinder now move upwardly in unison to lift the intermediate mast section, the inner mast section, an d the load carriage in unison at a 1 to 1 rate to the FIG. 13 position of the parts. The mast is now fully extended.

When pressure is released from the ram, the load carriage, the inner mast section, the intermediate mast section, the outer cylinder and the inner cylinder move downwardly in unison to the FIG. 10 position of the parts, at which time the latch mechanism 35 is operated in a manner to be explained hereinafter to release the inner mast section for downward movement relative to the intermediate mast section. Continued release of pressure from the ram results in lowering the inner mast section to the FIG. 7 position, at which time the latch mecha: nism 29 is actuated in a manner to be presently explained to release the load carriage for downward movement rela-. tive to the inner mast section, and the ram cylinder 23 is again latched to the inner mast section 15.

Detailed description Referring to FIGS. 2 and 6, the channels 11 of the outer mast section are joined at the lower ends thereof by a connecting piece 49 which supports the lower end of the ram plunger 17 as shown in FIG. 2. Projecting rearwardly from the lower end of the channel 11 are conventional split mounting blocks 50 for mounting on suitable shafts or axle structures on the frame of the truck to which the mast is applied. The channels 11 are also equipped with tilt cylinder brackets 51 of common design.

The upper ends of the channel 11 are connected by a composite brace structure 53 which is of angular form as shown in FIG. 3 to accommodate the upward movement of certain other parts as will be presently apparent.

The channels 13 of the intermediate mast section nest within the channels 11 of the outer mast section as shown in FIG. 3, and the channels 13 are joined at their lower ends by a crosspiece 55 best shown in FIGS. 2 and 3. This connecting piece is bowed forwardly to accommodate the ram upon upward movement of the intermediate mast section relative to the ram. The channels 13 are also connected at their upper ends by a brace 57 which is shown in FIGS. 3, 11 and 12 and which is of angular form to accommodate the upward movement of certain parts, and is itself accommodated for upward movement by the angular composite brace 53 as is apparent from FIG. 3. The brace 57 is important because it carries the stop 33 and the latch mechanism 35, as will be presently explained.

Referring to Fig. 3, the channels 15 of the inner mast section are disposed inwardly of the channels 13 of the intermediate mast section, and suitable rollers 58 are provided to guide the inner mast section upwardly relative to the intermediate mast section. The load carriage 27 has rearwardly projecting portions 59 carrying rollers 60 engaging the interior walls of the channels 15. Not all of the rollers for the load carriage or mast sections are shown, since the present invention does not lie in the details of this structure. The channels 15 are joined adjacent their lower endsby the brace 31, mentioned previously in connection with the operatiqner the device and which engages the stop 33, also previo sly mentioned. The brace 31 is also or angular form as best shown in FIG. 3 to accommodate the ram and also to be in position to engage the latch mechanism 35.

The channels 15 are also connected at approximately the mid port-ions thereof by a sheave supporting brace 61, which is best shown in FIGS. 2 and 3, and which is of angular form to accommodate the ram. The channels 15 are also joined at their upper ends by a sheave-supporting brace 63 which is of angular form to properly sup port a pair of sheaves 65 in desired positions relative to the ram as shown in FIG. 3. The brace 63 has forwardly projecting sheave supporting blocks .67 on which the sheaves are rotatably mounted.

Trained over the sheaves are a pair of lift chains 71 which are anchored at 73., as best shown in FIG. 1, to the load carriage 27. After passing over the sheaves 65 the chains extend downwardly and then upwardly around a pair of sheaves 75 mounted on the sheave supporting brace 61 as best shown in FIGS. 1, 2 and 3. The chains then pass upwardly and over a pair of; sheaves 77 mounted on the upper end ofv the outer cylinder 23 and then extend downwardly and under a pair of sheaves 79 mounted on the cross-head 2 1. The chains then extend upwardly and are anchored at 81 to a wing piece 83. The wing piece 83 is secured to the lower end of the outer cylinder 23 and has rabbeted edges 85 slidably engaging the inner edges of the rear flanges of the channels 15 of the inner mast section. The wing piece rest-rains the outer cylinder and therefore the ram against forward movement relative to the inner mast section under the influence of the weight of the load carriage 27 and its load, it being remembered that the outer cylinder is not secured at its upper end to the inner mast section, but only has a thrust n e on t r w th- Referring to FIGS. 3 and 4, there is also a vertical guide piece 91 secured at its opposite ends to the braces 61 and 63 and concealed behind the ram in FIG. 2. The outer cylinder has a slide 93, which is best shown in FIG. 4, secured to the upper end ofthe onter cylinder and through which the guide piece 91 s lidably extends. The guide and slide prevent rotation oi the outer cylinder 23 relative to the inner mast section channels 15 and also maintain the wing piece end portion in engagement with the rear flanges of the channels 15.

Carriage latch mechanism Referring to FIGS, 2, 3 and 4, the carriage latch mechanism 29 includes a hook element 101 fixed to the upper end of the outer cylinder 23 and having an upper hook portion 103 and a lower hook portion105. The upper hook portion 103 accommodates a roller 107 mounted on a lower carriage latch member 109 which is pivotally mounted on a shaft 111 which is mounted on the blocks 67 of the inner mast section brace 63. A spring 113 which is best shown in FIG. 3 urges the latch memher 109 in a counterclockwise direction as the parts are shown in FIG. 4, but the abutment of the roller 107 with a shelf portion 114 on the hook element 101 prevents such movement.

The hook portion -cooperates with a hook portion 115 on an upper carriage latch member 117 which is also 'pivotally mounted on the shaft 111 and is urged by a spring 119 in a clockwise direction as the parts are shown in FIG. 4 to maintain contact between the hook portions 105 and 1-15. It-is pointed out that the center of gravity of the latch member 117 as such as. to urge the latch member in a clockwise directienso that-even ii the spring 119 should break, the latch member 117 would remain in its operative operative position.

The latch member 117 also has a hook portion 121 which is disposed, as the parts are shown in FIG. 4, in position to be engaged by a latch tripping 'rod 123, which is best shown in FIG. 3,the rod being carried by blocks 125 of the carriage 27. Engagement of the rod with the hook portion 121 will pivot the latch member 117 in a counterclockwise direction, as shown in FIG. 8, until the latch member can pivot to more because of the fixed line of movement of the rod 123 and the approach of the rod 123 to the axis of the shaft 111. Thus the inner mast section is unlatched from the ram cylinder 23 because of the separation of the hook portions 105 and 115, and the carriage establishes a thrust connection with the inner mast section because of the engagement of the rod 123 with the hook portion 121 of the latch member 117.

To prevent the carriage from moving downwardly upon upward movement of the inner mast section relative to the ram, the lower latch member 109 is swung outwardly by the engagement of the roller 107 with the hook portion 103, as shown in FIG. 9, upon upward movement of the carriage relative to the hook element 101 to bring a hook portion 127 of the latch member'109 into engagement with the underside'of the rod 123. 'The hook portion !127 has a lower surface 129 of such configuration that although the hook portion can readily be swung into engagement with the rod 123, the rod cannot by its downward movement shove the latch member in a clockwise direction. To accomplish this, the surface 129 is made so that it forms an acute angle of slightly less than 90 degrees with a line extending through the pivotal axes of the latch member, that is through the axes of shaft 111, and the center of the rod 123. The acuate angle referred to is an upwardly facing acute angle as the parts are shown in FIG. 9. This means that the load carriage and its load are supported by the latch mechanism 29 against downward movement relative to the inner mast section until the latch mechanism 29 is tripped by an outside agency.

When the inner mast section and the carriage descend to the FIG. 9 position of the parts, the roller 107 will be brought into engagement with the shelf portion 114 of the hook element 101 to swing the latch member 109 in a clockwise direction and separate the hook portion 127 of the latch member from the carriage rod 123.

Also, such descending movement of the carriage from its FIG. 8 position to its FIG. 4 position will positively return the latch member 117 back to its operative position because of the engagement of the rod 111 with a surface 131 on the latch member 117. Thus the spring forces and the effect of gravity are not relied upon to cause operation of the latches.

Mast section latch mechanism Referring to FIGS. 1, 3, 11 and 12, the mast section latch mechanism 35 includes a latch member 151 pivotally mounted at 153 between a pair of depending arms 155 which are fixedly mounted on the brace 57, previously mentioned. A spring 157 urges the latch member to move in a counterclockwise direction, but a stop element 159 on the brace 53 of the outer mast section prevents such movement. Thus a hook 161 on the lower end of the latch member is held out of the line of travel of the lower brace 31 of the inner mast section.

However, there is the stop 33 carried by the brace 57 in a position to be engaged by the brace 31 upon upward movement of the brace 31. Thus the stop 33 and the brace 31 cooperate to lift the intermediate mast section upon upward movement of the inner mast section from the FIG. 11 position of the parts. Such further upward movement of the inner mast section, as is shown in FIG. 12, separates the latch member 151 from the stop element 159 and permits counterclockwise movement of the latch member 151 to its FIG. .12 position to engage under the brace 31. The surface 171 of the hook 161 is similar to the surface 129 on the hook portion 127 of the latch member 109 so that a downward force on the hook 161 by the brace 31 will only increase the hold of the hook on the brace. This means that an outside agency must move the latch member back to its initial position. This movement of the latch member back to its initial position is accomplished by the engagement of the latch member with the stop element 159 upon subsequent lowering movement of the intermediate mast section relative to the outer mast section.

Review of operation The general operation of the machine has been explained hereinbefore, and the specific operation of the latch mechanism 29 and 35 have been set forth above. One facet of the operation has not as yet been explained. Referring to FIG. 6, when the crosshead moves downwardly from the full line position shown in FIG. 6 to the dotted line position, the length of chain between a sheave 79 and a sheave 77 is increased, and the length of chain between a sheave 79 and the anchoring point of the chain on the outer cylinder 23 is increased. This means that the downward movement of the crosshead 21 from its full line position to its dotted line position increases the length of each of the chains just mentioned by an amount equal to the distance traveled by the crosshead. This results in a 2-to-1 movement of the loadcarriage 27 relative to the crosshead 21.

Referring to FIG. 7, when the outer cylinder 23 moves from its FIG. 6position to .its FIG. 7 position, there is a 2-to-1 ratio of the movement of the carriage 27 to the movement of the cylinder 23 because the same two lengths of chain are increased by the upward movement of the outer cylinder 23 as are increased by the downward movement of the crosshead 21. The upward movement of the inner mast section 15 is at a 1-to-1 rate at this time because the cylinder 23 is in direct thrust engagement with the inner mast section.

Movement of the outer cylinder 23 after release of the latch mechanism 23 connecting the inner mast section to the cylinder 23, will cause an in unison upward movement of the inner mast section 15 and the load carriage 27 at a 3-to-1 rate relative to the rate of movement of the cylinder 23. The reason for this is the continued lengthening of the two lengths of chain mentioned above and the decrease in the length of chain between a sheave 75 and a sheave 77.

Upward movement of the outer cylinder 23 and the intermediate cylinder 19 in unison from their FIG. 10 positions to their FIG. 13 positions merely results in a :l-to-l upward movement of the intermediate mast section, the inner mast section and the load carriage 27, because there is no change in the length of any portion of the chain.

Having described the invention in what is considered to be the preferred embodiment thereof, it is desired that it be understood that the invention is not to be limited other than by the provisions of the following claims.

I claim:

1. An extensible mast structure comprising at least three telescopically related sections, a hydraulic ram having a plurality of telescopically related tubular members, one of said members being movable downwardly upon the application of fluid under pressure to said ram, a second member being movable upwardly after said one member has moved downwardly, a load carriage movable along one of said sections, and means connected between said carriage and said one section and said ram for elevating said carriage upon downward movement of said one tubular member and for extending said mast structure and elevating said caniage during upward movement of said second tubular member, said second tubular member having a separable thrust connection with said one section to lift said one section upon upward movement of said second tubular member, and means latching said second tubular member to said one section to prevent upward movement of said one section during downward movement of said one tubular member.

2. A mast structure as set forth in claim 1 in which the connecting means is connected to said one tubular member and said second tubular member.

3. A mast structure as set forth in claim 1 in which there are reeving means on said one tubular member and also on said second tubular member, and in which the connecting means comprises flexible means anchored to said second tubular member and reeved under the firstmentioned reeving means and then over the second-mentione'd reeving means '"before extending to said one section and said carriage.

-4. A mast structure as set forth in claim 1 in which there are reeving means on said one tubular member and also on said second tubular member and in which there are lower reeving means on said one section and also upper reeving means on said one section, and in which said connecting means comprises flexible means anchored to said second tubular member and then reeved in continuous fashion under the first-mentioned reeving means and then over the second-mentioned reeving means and then under said lower reeving means and then over said upper reeving means and then anchored to said carriage,

5. An extensible mast structure comprising at least three telescopically related section, a-hydraulic ram having a plurality of telescopically related tubular members, one of said members being movable downwardly upon the application of fluid under pressure to said ram, a second member being movable upwardly after said one member hasmoved downwardly, a load carriage movable along one of said sections, and means connected between said'carr'iage and said one section and said ram for elevating said carriage upon downward movement of said one tubular member and for extending said mast structure and elevating said carriage during upward movement of said second tubular member, said second tubular memher having a separable thrust connection with said one section to lift saidone section upon upward movement of said second, tubular member, and means latching said second tubular member to said one section to prevent upward movement of said one section during downward --movement of said one tubular member, said load carriage being operable to release said latch mechanism when said load carriage is elevated a predetermined extent.

6. -An extensible mast structure comprising at least three telescopically related sections, a hydraulic ram having a plurality of telescopically related tubular members, one of said members being movable downwardly upon the application of fluid under pressure to said ram, a second member being movable upwardly after said one member has moved downwardly, a load carriage movable along one of said sections, and means connected between said carriage and said one section and said ram for elevating said carriage upon downward movement of said one tubular member and for extending said mast structure and elevating said carriage during upward movement of said second tubular member, said second tubular member having a separable thrust connection with said one section to lift said one section upon upward movement of said second tubular member, and means latching said second tubular member to said one section to prevent 8 upward movement of said one section downward movement of said one tubular member, said load carriage being operable to release said latch mechanism when said load carriage is elevated a predetermined "extent, said latch mechanism being operable to latch "said load car: riage to said one mast section when said load carriage is elevated a predetermined extent.

7. An extensible mast structure comprising at least three telescopically related sections, a hydraulic ram having a plurality of telescopically related members, one of said members being tubular and being movable downwardly upon the application of fluid under pressure to said ram, a second member being tubular and being movable upwardly after said one member has moved downwardly, a load carriage movable along one of said sections, and means for elevating said carriage upon downward movement of said one member and for extending said mast structure and elevating said carriage during upward movement of said second tubular member, said second tubular member having a separable thrust connection with said one mast section to lift said one mast section upon upward movement of said second tubular member, said one mast section having a thrust connection with another mast section upon predetermined upward movement of said one mast section relative to said another mast section, and means for latching said one mast section to said another mast section upon predetermined upward movement of said one mast section relative to said another mast section.

8. An extensible mast structure comprising at least three telescopically related sections, a-hydraulic ram hav-, ing a plurality of telescopically related tubular members, one of said members being movable downwardly upon the application of fluid under pressure to said ram, a second member being movable upwardly after said one member has moved downwardly, a load carriage movable along one of said sections, and means connected between said carriage and said one section and said ram for elevating said carriage upo'n downward movement of said one tubular member and for extending said mast structure and elevating said carriage during upward movement of said second tubular member, said second tubular memher having a separable thrust connection with said one section to lift said one section upon upward movement of said second tubular member, there being reeving means on said one tubular member and also on said second tubular member and there being lower reeving means on said one section and also upper reeving means on said one section, said connecting means comprising flexible means anchored to said second tubular member and then reeved in continuous fashion under the first-mentioned reeving means and then over the second-mentioned reeving means and then under said lower reeving means and then over said upper reeving means and then anchored to said carriage.

References Cited in the file of this patent UNITED STATES PATENTS 2,595,959 Lawless May 6, 1952 2,670,811 Shaffer Mar. 2, 1954 2,877,868 Gunning 17, 1959 2,906,373 Hastings Sept. 29, 1959 FOREIGN PATENTS 62,888 France Feb. 16, 1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,987,140 June 6 1961 John E. Olson It is hereby c ent requiring corre corrected below.

ertified that error appears in the above numbered patction and that the said Letters Patent should read as Column 1, lines 19 and 20 for "structurues" read structures column 1, line 741, for "as such" read is such column 5, line 10, for "to" read no line 3 1, for "acuate" read acute column 7, line 30 for "section" read sections Signed and sealed this 7th day of November 1961.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC 

